At the time of writing The IPv4 Depletion Site estimates there are 300 days remaining before all IPv4 addresses have been allocated. I've been following the depletion of IPv4 addresses for some time and realize the "crisis" has been going on for many years and IPv4 addresses have lasted longer than expected, however...

As the systems administrator for a small SaaS / website hosting company, what steps should I be taking to prepare for IPv6? We run a handful of CentOS and Ubuntu Linux systems on managed hardware in a remote datacenter. All our servers have IPv6 addresses but they appear to be link local addresses.

Our primary business function is website hosting on a proprietary website CMS system. One of my concerns is SSL certificates; at the moment every customer with an SSL certificate gets a dedicated IPv4 IP address. What else should I be concerned about / what action should I take to be prepared for IPv4 depletion?

I suggest that hosting company needs to upgrade their Server Load Balancer (SLB) equipment to IPv6 support. It will ease IPv6 deployment (SLB will give you virtual IPv6 address and either v6-v4 (dual stack) reals server, v6-only reals server, and v4-only reals server).

I have evaluated one of the SLB from Brocade (ADX1000) that give you IPv6 SLB, and you can easily make your existing IPv4-only server to give IPv6 services via SLB without (almost) any configuration on your existing server.